Planet Four Talk

The Heart of the Matter

  • wassock by wassock moderator

    Or why are the spiders not everywhere II

    Observe these 4 images from 2007,2009,2010 & 2012 The solar longitude for each is between 173 and 186 dgrees so vaguely the same time of year

    enter image description here
    enter image description here
    ![enter image description here]
    (https://dl.dropbox.com/s/5wayhdpqsb91hg1/20101114_181_ESP_020163_0980_red_jp2_TheHeart.png)
    ![enter image description here]
    (https://dl.dropbox.com/s/bv2resi7bvv59zo/20120917_173_ESP_028800_0980_red_jp2_TheHeart.png)
    The last one's scaled wrong will try to fix link to it here: https://www.dropbox.com/s/bv2resi7bvv59zo/20120917_173_ESP_028800_0980_red_jp2_TheHeart.png

    OK So The pattern of fans repeats every year in the same places. The area between contains spiders (and bugs) but no fans form there.

    The position of the individual fans appears to be remarkably consistent, look particularly at the round blob but there seem to be consistent fans in the heart as well - will need to do some careful scaling to confirm this.

    SO. If the spiders form the fans why are the fans not everywhere? If the fans form the spiders where did the ones without fans come from?

    In the last image the spiders in the Heart are much better defined than those outside it, anyone have any suggestions why?

    Is it possible that only the areas with fans are actually covered with ice, or could it be that the ice layer is thinner/thicker there?

    Next step try to find the area on a altitude plot to see if the level of the land has anything to do with this.

    NB the wind direction appears consistent across the 4 years - there are other images which do show a variation of direction, but they all appear to be steady in a given year - no multiple fans here.

    Posted

  • wassock by wassock moderator

    Meg/Anya/Candy - there are an awful lot of images of this area available - has someone already covered this angle?

    Posted

  • Kitharode by Kitharode moderator

    Latitude / Longitude? Might have to wait till Monday for a scientist.

    Posted

  • Portyankina by Portyankina scientist

    Hi!

    One of my own unresolved questions.
    I am sure in one thing: more fans lead to more erosion, lead to steeper walls of spider channels. Kind of positive feedback loop. But why it stopped in some locations and continued in others? The topo of this location (as far as I recall) is rather flat.

    Anya

    Posted

  • Kitharode by Kitharode moderator in response to Portyankina's comment.

    Hi Anya!

    So is it now a fact, more fans=more erosion=steeper walls, or are just sure in your own mind? I thought 'growth' of spiders was still under debate. Would be good if we knew for sure.

    Posted

  • wassock by wassock moderator

    Kith if you want to find the originals just bang the esp_012345 bit into HiRise or go here http://hirise.lpl.arizona.edu/ESP_029710_0980

    Anya only said she believes the bit about erosion not that she knows it to be the answer

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    Wassock: You didn't give the esp_012345 numbers, so how do I find them? I've not got my head around tracking images yet.

    I'd a feeling Anya's was a personal view, but wanted to check because it's important methinks.

    I went to the link in your post above and got the RGB non-map thingy and got distracted by the 'dinasaurs' there. I've met these before and they weren't venting either, even though they are next to proper spiders. Here's one of them being approached by a large dendritic; http://planetfour.org/subjects/standard/50e73d835e2ed2124000138e.jpg

    I've a few more of these dinasaur images and they all look the same; old, washed out, 'fossilised', like dinasaurs. And they're BIG, as you can see. Now being in such close proximity to proper spiders it strikes me that there's some relationship between them, be it a geology thing or a time thing, or a something. Are we looking at pockets of dust that can be used by a spider, but can also be used up by a spider? Having formed and branched out, when the ends of the legs 'run out of fuel' the spider then uses up the centre of the dust patch then fizzles out. Then it gets worn down with age.

    Or maybe that's nonsense! Here's some more dinasaurs anyway: http://planetfour.org/subjects/standard/50e73e235e2ed211dc001302.jpg

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    I imagine there are lots of images because this one of the regions in the seasonal monitoring campaign so there are lots of images taken throughout a Martian Spring and Summer and then targeted again years 2, 3, and. 4 with similar cadences.

    Cheers,

    ~Meg

    Posted

  • wassock by wassock moderator

    Meg - Figured that, just seem to be more of this specific bit than I've found for other areas I've tried looking at a sequence of images for. Given that what I'm looking at seems like a fairly obvious question I just wanted to check that this 'ground' hadn't been covered before. Is there anything on the satellites which can monitor ground temperature on a small enough scale to see if there's a temperature difference between the Heart and its surroundings?

    Do you have any other sites which show, as this seems to, repeated fans from the same source points year after year? I've tried looking before but not found any.

    Kith - yerse sorry, I can see the links but you can't, Dhoh!. The Lat is around -81.693 and the long 69.306 - search HiRise for those +- .2 and you'll find a whole bunch. These images are cropped from the Hires JP2 files but you can get a good Idea of wha'ts going on just from the grey jpgs. It's the same area as in the "Crater....." thread, a feature which also warrants looking at a bit more http://talk.planetfour.org/#/boards/BPF0000009/discussions/DPF0000ckr

    wrt Dinasaurs - they look like big 'bugs' to me, but indicate that more erosion equals wider rather than deeper - which kinda makes sense. I f we have a gully with a layer of dust at the bottom which gets blown along, all the time theres a layer of (mostly still frozen maybe) dust in the bottom it will protect what's underneath from erosion and by the time the bottom is exposed, there's no dust left, so the sides get worn more than the bottom? Assuming that dust/fans is what made them in the first place that is. Doesn't explain why they seem to 'switch off' though.

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    We'll need the exact classifications for those images to really show they are coming from the same spots. They very may be a slightly different positions, but close to being on top of each other.. There are differences in the numbers of fans present from Year 1 to Year 2. Part of examining exactly where fans repeat is part of the science goals of the project I believe. But clearly here, now that there's 2 spiders that's where the fans all are, so before the spider formation there probably weren't fans? definitely an interesting find. I think the analysis of the bulk classifications of markings will hopefully help start to fill in this picture.

    Also different regions may have different cadences. Candy, Anya, and K-Michael can probably talk more about that.

    But you can see on the blog an area where blotches and fan appear in similar area.

    Cheers,

    ~Meg

    Posted

  • Kitharode by Kitharode moderator in response to mschwamb's comment.

    Meg: How are you using the term 'cadence' here? I'm familiar with the musical cadence, but not the martian one. Can I play it on my guitar? 😃

    Posted

  • mschwamb by mschwamb scientist, translator in response to Kitharode's comment.

    observing cadence = how frequently images are repeated

    Posted

  • wassock by wassock moderator in response to mschwamb's comment.

    Hi Meg the area in your link is the one I refer to in the 'bendy winds' thread - the fans seem to follow curves. It's also one of the areas where I tried to find repeating fans - it's a big area, so more difficult to focus, but I couldn't see any that looked like they repeat. Whereas with the Heart and particularly the spot nearbye there are several which do seem to repeat, but as you say will need some careful measuring to confirm

    Posted

  • wassock by wassock moderator

    Here's the dot in summer, cropped from the large hirise image. Was hoping to see some obvious boulders or such which would give a start point for repeating fans

    enter image description here

    Posted

  • wassock by wassock moderator

    Some more observations of the 4 heart images above:
    Across the 4 years the size of the fans stays fairly constant both between years and across the spider system they all share.
    The distribution of fans appears to be denser on the edge of the spider (although this may just be an illusion due to the edge)
    The spiders in the fan forming area are much more defined than the 'washed out' ones
    The spider system has the classic morphology of branching channels which get smaller the further from the center

    So how does this fit the standard model of spider/fan formation?
    If the spider channels are the distribution network/reservoir for the dust in the fans then it should be that the fans on or close by the wider channels should be larger than those on the rim which are only fed by thin channels. This doesn't seem to be the case here,and if anything there seems to be more dust coming from the rim than the middle.
    If there are regularly lots of fans on the edge then there should be "lots" of erosion in the channels leading to them - this is not what is observed, the channels get thinner as the approach the rim.

    Posted

  • p.titchin by p.titchin in response to wassock's comment.

    The RGP col strip for APF00013z8 shows another area of these lovely crisp 'starburst' spiders with adjacent, but not joined broad shallow spiders (?Kith's 'dinasaurs'). ~Pete

    Posted

  • wassock by wassock moderator in response to p.titchin's comment.

    That's the same area as all the above Pete - check the greyscale image

    Posted

  • wassock by wassock moderator

    So here we have a crater bottom, Fans, polygonal cracks - NO Spiders

    enter image description here

    And at the North Pole http://hirise.lpl.arizona.edu/ESP_017092_2515

    Posted

  • wassock by wassock moderator

    North Pole again,bear with me

    These look like Dunes - formed by the wind - image is August 2008

    enter image description here

    This one is October 2010

    enter image description here

    So has the wind stopped blowing?

    Posted

  • p.titchin by p.titchin in response to wassock's comment.

    ? permafrost cementing surface? How the questions keep coming!

    Posted

  • wassock by wassock moderator

    Point being that clearly at some stage they were moved by the wind, , now nothing happens in 2 years. So does it take a very long time to form a sand dune, in the same way that it appears to take a very long time to form a spider?
    Or were these things just formed a very long time ago?

    Posted

  • Kitharode by Kitharode moderator

    I'll pass on the northern dunes. Not enough room in my head at the moment, but it's an interesting question. 😃

    Going back to the Heart of the matter, I did some plots on wassock's initial images. Rather than try to plot them all, I did about a 120 or so of the same fans in each image. I chose small shapes inside the 'heart' that were easily seen in all images; 'that triangle', 'that square', the curve, the star shape, etc.

    Allowing for inevitable inaccuracies on my part, the results are interesting if nothing else. If I make a 'perfect' match in the centre of the heart, there is an increasing mis-match towards the edges. Shifting my plots one way or the other, I can get perfect alignment of a shape at that edge, but the middle is now out of phase. It is easier to accept that the scale between images is 1 or 2% out, rather than accept a growth in the extent of the heart.

    If there was growth in the heart, then it's surprising that all four corners of 'that square' at the top all move in the same upwards direction by the same amount, whilst the points of 'that triangle' at the bottom are all moving down by the same amount. Similarly with shapes at the other edges.

    Without precise measurements we can't be sure, but there is much to suggest that the vents do repeat in the same place. Wassock has raised some seriously good questions here and I hope we'll learn more about the Heart.

    Posted

  • wassock by wassock moderator

    The small do to the side of the heart may be easier to deal with, I'm reasonably sure that there are some (not all) repeaters there but there doesn't seem to be any obvious start point for any of them - a boulder, bend in the leg of the spider or such. But other than the spiders being different/cleaner where the fans are forming I don't see anything which supports there being a causal relationship between the spiders and the fans anywhere. One reason I've seen for no fans up north is in part the shifting nature of the terrain up there, but it's not shifting much, even though many of the dunes show marking from dust devils each year..
    Sure we get spiders associated with fans but we also get spiders where there are no fans and fans where there are no spiders. And the way the spiders form on the heart, to my mind, runs counter to the 'standard theory' in that the fans have a consistent size across the area of the heart and there seems to be a higher concentration at the rim. My interpretation of how it's supposed to work would give larger fans near the middle and fewer out at the edge.

    Kith for you to get a perfect match the satellite would have to be in exactly the same place for each photo, if it's even slightly out of position the appearance is going to shift and the effect will be greater at the edges of the field of view and amplified by any altitude changes going on at the surface. How does the satellite orbit, is it a perfect circle or elliptical, meaning the the photos will be taken at varying heights?

    Posted

  • Kitharode by Kitharode moderator

    Taking another look at the 'Science of the HiRise Camera' paper, it would appear that the MRO is in a 'standard' elliptical orbit of 255 x 320km. If there is no precession of the orbit then the height at each pass will remain constant. The technical stuff in the paper describing the camera's capabilities is beyond me, but I'd be surprised if two passes over the same area produced precisely the same image. This is not to say that differences cannot be tracked and recorded. If that's the case, the techies may well be able to 'rub out' the differences later.

    Spider formation 'standard theory' is beginning to creak a little of late, certainly for some areas. Can we do better though? 😉

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    Given that it appears that change on the surface, on a scale that we can see over a 5-6 year time interval, is a fairly rare occurrence (even in fields of apparently wind blown dunes) and that most features (like the water carved channels) have been there for a very, very long time. Perhaps the same is true of the spiders?

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    I have no problem at all with the idea of the spiders being very, very old. The thought has passed through my mind, but I don't know what to do with it. 😃

    We might get a handle on how old they could be if we can find an age for the surface they're on/in. That is, if a spider is in the top layer of the SPLD and we can get an age for that, then that would give us an age limit for said spider (I think).

    But does it change anything if spiders are relatively old? I think that's where I get stuck.

    Posted

  • wassock by wassock moderator

    Just means we don't have to invlude a mechanism for making the spiders in the one for forming the fans

    Posted

  • Kitharode by Kitharode moderator

    OK, I see what you're saying. We'd have to be sure that venting fans do not have a role to play in spider formation. Maybe the fan process is older than the spiders! (I'm not happy with that idea). I think SPLD's and obliquity would be important considerations if large timescales are involved.

    It does seem that a case could be made to show that fans and spiders are not as intimately linked as the 'standard theory' seems to suggest. On first arriving at Planet Four my initial understanding was 'fans make spiders', but clearly it is not as simple as that. Perhaps 'fans keep spiders clean' might apply? It seems clear enough that some types of spidering (chains, lace, etc) are more likely to be the result of freeze/thaw or contraction of ground/ice, etc, rather than the result of venting/scraping.

    The 'standard theory' is still a good theory for explaining venting and fans, but I agree with you that it doesn't need to include spider formation, growth and longevity. So how do we go about making sense of this (rather exciting) idea?

    Posted

  • wassock by wassock moderator

    It also means that we wouldn't have to fret about how the fans manage to generate such a menagerie of different spider types. Wouldn't stop the spiders helping the fans along but neither would require the other in order to exist (which they don't).
    It also solves the problem of why there are no spiders at the North, even though there are fans. Reason for this given so far is that the terrain is different/doesn't lend itself to spider formation. Turn that around an it becomes the terrain is different (as it is newer?) and therefore contains no spiders (and the fans dont care)

    Posted

  • Kitharode by Kitharode moderator

    And another thing: How would fans make different spiders, in the same place, over the same period of time? It seems more likely that geology/surface composition/topography could achieve this, rather than venting fans (?)

    Don't know the lat/long for this image, but it's HiRise south polar: https://www.dropbox.com/lightbox/home/Mixed Spiders and there are lots of other examples.

    OOPS. We crossed over !!

    Posted

  • wassock by wassock moderator

    The link's not working Kith

    Posted

  • Kitharode by Kitharode moderator

    Sorry. Some do some don't. 😦 Anyway it's an image with different shaped spiders at top and bottom. (I'll try again later).

    Timescales: It strikes me that if we're moving towards the idea that fans don't make spiders, but other things do, then the spiders don't have to be old features. They might be, but they could equally be young. Fans/no fans would make no difference.

    Posted

  • PaulMetcalfe by PaulMetcalfe

    I would just like to throw one of my not fully worked out ideas into the mix. For ease of description I will call fans low-pressure release points and spiders high-pressure release points that are only connected in the sense that they release gas/material into the atmosphere. The low pressure being like a leaky valve allowing the particles to escape and be blown with the wind in a gentle way.
    The spiders remind me of 'volcanoes' but sitting on top of reservoirs of gas (or something). When frozen the system is sealed and as it warms or pressure gets high it leaks out of the legs (sometimes as a fan and sometimes as a splatter). At the same time the iced in top of the spider is being forced out and eventually launches into the air releasing one big splatter of material all around and over the spider. The ejected plug may travel near or far or even disintegrate. It is only one idea and not fully researched yet but any comment is welcome.

    Posted

  • Kitharode by Kitharode moderator

    I will say that it's good to see you having a serious think about the situation. Sounds like you're proposing a variation on the 'standard theory'. You've probably already seen that, but for any newcomers it's here: http://planetfour.org/#/about

    The 'splatter' doesn't feel like a good idea to me, but there again, what do I know? 😃 Perhaps you should have a dig around the images and see if there's anything that looks like splatter in/near the spiders. Who knows, you might find loads of it. I've never looked for ejecta near spiders so perhaps it's there and I didn't take note of it.

    Seems to me that you'll need a couple of image examples to support your ideas, whatever area you're looking at. It'd also help us to see more clearly what you're telling us. Good hunting. 😉

    Posted

  • wassock by wassock moderator

    Paul, you've got some crossed terminology above. The spiders are surface features, cut into the rock/dust/whatever of the planet and are there wether there is ice or no. Fans and blotches are on top of the ice layer and made of dust (probably) ejected through the ice, and they vanish when there is no ice. Fans being formed when there is a wind and blotches in still air conditions. Tricky bit is how the stuff is ejected, how fast, how much pressure, how we get separate fans from the same vent, why there are different colour effects and do the fans form the spiders and are all the spider types related (have common formation mechanism)?

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    Going back to the 'big bugs' with no fans. The question is: Why do the fans 'switch off'? One possible answer must be: They don't switch off because they never had fans in the first place and they're not really bugs (spider channels).

    The more I look at them the more they don't look like 'scraped depressions', especially in the HiRise greyscale collection.

    Saw something recently (somewhere) about 'thermal waves'. I think it's like a 'wave front' travelling through the ground, connected to thermal inertia (?) Might possibly have a part to play in features at the surface. Do you know owt about it?

    Posted

  • wassock by wassock moderator in response to PaulMetcalfe's comment.

    The miracle that is google reveals lots of stuff about thermal tides but it's all about atmospheric effects this one is top of the list http://onlinelibrary.wiley.com/doi/10.1029/1999JE001161/abstract but the abstract won't be winning any awards from the plain English society

    Posted

  • p.titchin by p.titchin

    Paul, are what you are calling 'ice plugs' the rounded white 'boulders'/ 'snowballs' we see? ~Pete

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to p.titchin's comment.

    I am not saying that they are, just that they could be. It is only one 'complicated facet' of an initial idea that I am exploring. I would not even assume at this stage that all snow-balls were ice-plugs even if some were proved to be.
    Paul

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    You're right about the (non) plain English - Phew. 😃 The atmosphere obviously has a part to play in the overall scheme of things, but I don't think we need invoke it for the questions raised here.

    Perhaps 'thermal front' might be a better term for me to use. I'm thinking that as Spring progresses the icelayer retreats and the ground gets 'warmer'. At the same time, according to theory, we have a warming of the surface where ice still exists. This leads me to thinking about this 'thermal front' that would be moving poleward beneath the icelayer. Put simply, it gets warmer underneath and stays cold on top.

    Could this produce a thermal gradient in the top few metres of the surface, large enough to affect surface structure, over and above the sublimation of co2 ice and loosening of dust? Probably safe to say 'yes' because we see it elsewhere. If there be any truth in any of that, then maybe 'fans exploit spiders' is a workable idea.

    Or perhaps I've had too much coffee ... 😉

    Posted

  • p.titchin by p.titchin in response to p.titchin's comment.

    I have much to say on the plugs Paul, I think that (like Wassock) we need to get of his thread. Great if you start one on 'citizen science ' so we can chew this one--- Join you there when you post~~Pete

    Posted

  • Kitharode by Kitharode moderator

    Thanks guys. I've got an image to post if you do start an 'ice plugs' discussion - see you there.

    Wassock: Regarding my 'thermal front'. I'm bearing in mind some of the stuff we talked about in 'Spiders by Latitude'. I'd done some back of the envelope estimates about the retreat of the icelayer in Spring. I suggested that by early Spring (when the fans start fanning) the icelayer might have retreated from around latitude -60deg to around -70 or so, close to the edge of the spider forming region (roughly -75 to -85deg).

    The relative warmth of the ground where the icelayer was, coupled with the warming surface where the icelayer is, is where my thermal front would be.

    I'll have another brew..... 😉

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to Kitharode's comment.

    I believe there may be merit in your (it gets warmer underneath and stays cold on top) theory, that should be kept in mind. It is on my 'To check out list'.

    Posted

  • PaulMetcalfe by PaulMetcalfe in response to p.titchin's comment.

    Pete: Ice plugs do represent part of my theory but my main opening consideration would be the initial spider formation. I could of course start two threads as I do not think 'ice plugs' would only be confined to spiders or you could start a specific thread on that.

    Paul

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    Kith there's a paper/post somewhere that talks about the release of thermal energy from the ground beneath the ice - the layer forms over the ground before it has cooled down so you have a sort of inverted baked Alaska. means you have a large heat sink under the initial ice layer

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    Thanks. I'll try and dig it out. A question that springs to mind is; How does ice form on a surface that is warm enough to sublime it? Is it because the heat sink is lower down and is 'sealed in' by a cooling surface and has to work it's way back up?

    Can you remember a title/author for the paper you mention?

    Posted

  • wassock by wassock moderator

    THink the very surface may be cold but a little way down there's still stored heat. Think it was a post somewhere in a thread, someone talking about inrared warming the ice from beneath. Maybe also a paper I saw which was proposing a continuous outgassing cause for the fans

    Posted

  • Kitharode by Kitharode moderator

    This is from the same area, so sorry if it's already been posted. But it's a good image to better illustrate what I said earlier, about the big bugs possibly not being bugs. What I see here are bug shaped depressions to be sure, but they look to have more to do with geology than spidering. Yes there's an occasional fan associated here and there, but there's nowt strange about that.

    There's some good evidence to suggest that large numbers of dentritics can be found in large depressed areas, valleys, and such like. If this is true, and the bugs are not bugs, two things spring to mind. Firstly, we wouldn't need a 'switch off' mechanism for the bugs because they were never switched on to start with. Secondly, objects like 'the Heart' might provide clues to the local topography.

    Or should I stick to playing guitar? 😃

    Posted

  • wassock by wassock moderator

    No pic Kith!

    Posted

  • Kitharode by Kitharode moderator

    Oops http://hirise.lpl.arizona.edu/ESP_020677_0980 😃

    Posted

  • Kitharode by Kitharode moderator

    PS: I'm now convinced that the 'bugs' in this area are not bugs. I'm going with erosion of SPLD edges.

    Posted

  • wassock by wassock moderator

    And on to the Heart in my current theme of "what lies beneath?"

    Hi rise give lat/long as -81.7/66.3(E) which as I read the spld map puts it close to the edge. On the albedo map thats close to Giza (about -85/66) where the yardangs are, which I read as on the pld?

    enter image description here

    enter image description here

    Posted

  • Kitharode by Kitharode moderator

    Sorry. Heads full and losing it slightly, so...

    Are you talking specifically about your 'Heart formation' being at -81/66 and this would seem to be near the spld edge, but not on the spld? If so, looks that way to me.

    Likewise, If you see Giza at -85/66 being on the spld then again I'd agree. The two locations are relatively close by.

    Which means ... ? 😃

    Posted

  • wassock by wassock moderator

    If the surface is Mars then its hard(ish) maybe, with a fairly thin layer of grust. If its the top of the levels then it is a frozen slush puppy of ice and wind blown dust, so what goes on ought to be different.

    Posted

  • Kitharode by Kitharode moderator

    Yes, I agree. I've often thought this should be the case, even though I've never really considered exactly how they would be different. That's why I sometimes ask for lat/long on objects, to see if they're on/off the spld. My thinking was that if I got enough 'ons' and 'offs' I'd spot something.

    Maybe I need a new plan ... 😃

    Posted

  • wassock by wassock moderator

    One idea would be that the more ice there is beneath the surface then the more likely there will be cracking on the surface, The problem I'm finding is that a lot of the "interesting" areas lie close to the edge so it's hard to know if they are on or off. So if you look at the two maps above and the location of Manhatten, you can't tell if it's on or off or half way

    Posted

  • Kitharode by Kitharode moderator

    If I can find my Mars DVD of cartographic maps I'll see if I can get a more accurate fix on this. Problem at the moment is that I've put it somewhere safe, but not somewhere findable !! (rummage rummage)

    Posted

  • wassock by wassock moderator

    This Years model http://www.uahirise.org/ESP_037859_0980

    So thats 5 seasons in a row we get the same pattern of fans across a large area

    enter image description here

    And in colour

    enter image description here

    Posted

  • wassock by wassock moderator

    The bigger Picture

    2009

    enter image description here

    2014

    enter image description here

    Posted

  • Kitharode by Kitharode moderator in response to wassock's comment.

    Images not showing. 😦

    Posted

  • wassock by wassock moderator

    Which ones Kith? they work for me.

    Posted

  • Kitharode by Kitharode moderator

    OK now. Must be my broadband playing up again.

    Following your 'This years image' a couple of posts previously, and looking at the Jpeg non-map image, there's an interesting circular(ish) feature about a third of the way down on the left hand edge. The surrounding area looks a bit like the 'fried egg' ejecta blanket often seen around some craters on Mars, but the circle don't look like a crater.

    Re The Heart; Got any theories yet about what's going on?

    Posted

  • wassock by wassock moderator

    It's a crater, found that before I noticed the other stuff going on see http://talk.planetfour.org/#/boards/BPF0000009/discussions/DPF0000ckr

    No idea what's going on but it seems clear that the presence of a spider does not mean that a fan will form. The position of the individual fans seems to vary but the shape/position of the islands doesn't. I wonder if these are high/low spots in the terrain but it's not obvious. Or theres some sort of difference in the ice layer. Note that the direction of the fans is very consistent year on year

    Posted

  • Emberfire by Emberfire

    2 theories:

    1. Could it be that these fans are formed in an old crater.
      When the crater is formed, we know they often get filled with "Material" often of a different type to the ground parent material.
      Could this material be forming lakes in the craters of material (dark stuff) that boils off in certain conditions. Causing formal pattern of vents.

    2. If the crater is formed by lava tubes, hot material bubbling up from under the ice, then only where the tubes come to the surface would you get clusters of vents.

    Posted

  • wassock by wassock moderator

    OK new perspective on this from the CRISM spectral data

    1st image Solar Longitude 250 20/4/09 early season not many fans

    enter image description here

    and SL 263 11/5/09 (slightly larger scale - lots of fans

    enter image description here

    The 'waist' in both is in the same position relative to what's around it. Clearly something has changed. The colours are telling us something about waterice/mineral bound water but I'm not sure what.

    LOTs of images of this available so I assume that someone somewhere has been having a good look at this already.

    enter image description here

    Posted

  • mschwamb by mschwamb scientist, translator in response to Emberfire's comment.

    Hi Emberfire,

    One thing to consider is that whatever is weakest the carbon dioxide gas will exploit first to carve the spiders into. So if the material in the craters is different or weaker than the surrounding terrain regolith, you'll preferentially get spiders in the crater material and the fan production.

    Cheers,
    ~Meg

    Posted

  • mschwamb by mschwamb scientist, translator in response to wassock's comment.

    Hi Wassock,

    Likely amount of water ice or carbon dioxide ice, but you have to make sure the color scales are really the same and normalized differently. I've never used CRISM data, so I'm not much help here. I'll see if Anya or Candy have time to take a look. I believe they've used CRISM in the recent past.

    ~Meg

    Posted

  • wassock by wassock moderator

    Thanks Meg, the main point of this whole thread is that the whole area is covered in spiders but only some of them produce fans. The fan producers are sharp and well defined but the ones which don't have a 'worn out' appearance. In the image above the blue area is where we have no fans and the pinky/purple bit is where the fans form. So something different happening in the 2 areas, which could just be that the dust from the fans is covering up the 'blue signature' of what lies beneath

    Posted